Alcohols are versatile organic compounds reagents and can be used as precursors for other classes of organic molecules in synthetic chemistry. Catalytic hydrogenolysis of C═OH bonds is a very important synthetic technique; it is widely used in organic synthesis [1-3], pharmaceutical production [4,5] and biomass conversion [6-8]. Reduction of alcohols to the corresponding hydrocarbon is usually accomplished sequence of steps. Conventionally, hydrogenolysis of C═OH bond is achieved with molecular hydrogen using noble metals as catalysts. In some cases, stoichiometric reducing agents such as metal hydrides are used. Nevertheless, these traditional hydrogenolysis methods have some drawbacks. One drawback is the use of molecular hydrogen or stoichiometric reducing agents that often causes safety and environmental problems, because molecular hydrogen and metal hydrides are flammable, explosive and hazardous. Another drawback is the use of high temperature and high-pressure that will necessitate expensive high-pressure equipment, thereby increasing the cost of the process and resulting in many troubles in manipulation. An additional drawback is its low selectivity due to the hash reaction conditions employed. In contrast to the traditional hydrogenolysis methods, catalytic transfer hydrogenolysis (CTH) uses hydrogen donors to provide hydrogen species in situ; hence it offers the possibility to overcome the drawbacks of the traditional hydrogenolysis methods.
CTH is an important synthetic technique in organic chemistry. As neither hydrogen containment nor a pressure vessel is required; the mild reaction conditions offer considerable advantages over the conventional method of catalytic hydrogenolysis. For the transfer hydrogenolysis or hydrogenation, it is necessary to select an efficient catalyst and suitable hydrogen donors. Recently, formic acid has been employed as the source of hydrogen and has many advantages in regards to handling, transport, and storage and can easily be generated form hydrogen gas and carbon dioxide.
Generally, metal (VIII group elements) such as palladium ruthenium and Raney nickel are employed as the catalysts for the transfer hydrogenolysis. Palladium is arguably one of the most powerful and versatile transition-metal catalysts which can be immobilized on various heterogeneous supports and be used for a variety of organic transformations. Palladium heterogeneous catalyst can be recycled by simple filtration and reused in several cycles without the loss of efficiency with the consequently advantages such as economic and environmental. Recently, we developed asymmetric carbocyclizations implementing a heterogeneous palladium catalyst with a simple chiral amine co-catalyst. However, it is not sure whether the Palladium heterogeneous catalyst could be reused for the CTH of alcohols.